Questions on operating a nuclear power plant on the Moon or Mars

[KurtLudwig]

Heat cannot be removed by liquid-to-gas heat exchangers since there is no substantial atmospheres on the Moon or on Mars. It cannot be dissipated by venting steam since there is a critical water shortage. It cannot be dissipated by rocks or soil since both are essentially thermal insulators. It appears heat can only be dissipated by liquid-to-thermal radiation. Without having done any calculations, these heat exchangers will be huge to radiate heat generated by nuclear power plant.
I tend to believe that solar panels on the Moon is a much more reasonable solution to power generation. The drawback is that electric energy will need to be stored in Lithium-ion batteries to supply electricity during the lunar night of 14 days.

 

[berkeman]

It cannot be dissipated by rocks or soil since both are essentially thermal insulators.

I guess you mean dry soil? Soil on the Earth is a pretty good thermal conductor, I believe, but I guess that is just because of the moisture in the soil?

 

[hmmm27]

Don't get me wrong : I'm all in favour of solar power anywhere there's a solar - including extraterrestrial operations - but ... you do realize PV panels are only 20% efficient at best, right ? and that's at 30C. Where does the other 80% go ?

 

[PeroK]

Summary:: It has been proposed to operate nuclear power plants on the Moon and on Mars.

How do you build a nuclear power planet on the Moon or Mars?

 

[Nugatory]

It has been proposed to operate nuclear power plants on the Moon and on Mars.

Proposed by whom? And to what purpose? “Nuclear power plants” is not very specific. It’s hard to comment sensibly without knowing what is being proposed and why.

 

[KurtLudwig]

Electric power will be needed when man and women settle on the Moon or Mars. I have read read in magazine articles and on the Internet that small nuclear power plants have been proposed to produce electric power.
The main question on this post is: How can heat be removed from such nuclear power plants? As on earth, nuclear power plants need heat to be removed to operate. The only option I know of is by radiation.

 

[anorlunda]

Power can be radiated out to space.

The moon's surface is warmed when facing the sun, and it cools when in the shade. The energy lost during cooling is radiated into space.

After we succeed in transporting 1 ton of stuff to Mars, how long do you expect it to take to transport a million tons to Mars? a billion tons?

 

[gmax137]

Proposed by whom? And to what purpose? “Nuclear power plants” is not very specific. It’s hard to comment sensibly without knowing what is being proposed and why.

Exactly, there is a huge difference between a radioisotope thermoelectric generator making a couple hundred watts and a 1 GWe "power plant."

 

[jbriggs444]

Rough order of magnitude, the sun radiates the surface of the Earth or moon with about one kilowatt per square meter. It follows that one square meter of Earth or moon surface can radiate one kilowatt to space at a moderate temperature.

So, rough order of magnitude, we need a one kilometer square footprint to dump heat from a 1 GW plant.

 

[DrStupid]

So, rough order of magnitude, we need a one kilometer square footprint to dump heat from a 1 GW plant.

That's at least the same order of magnitude as for the TOPAZ II reactor. It had an electrical power of 6 kW with 7.2 m² radiator area (according to https://www.osti.gov/servlets/purl/10151265). That corresponds to 1.2 km²/GW. As the efficiency was just around 5 %, there is a possibility to reduce the area by upscaling and with a modern design. But I don't expect it to be much less than 1 km².

For comparison: The solar arrays of the ISS have an area of 2500 m² and can generate 84 to 120 kW of electricity energy (according to https://www.nasa.gov/mission_pages/station/structure/elements/solar_arrays-about.html). That corresponds to 21...30 km²/GW. On Mars it would be much more due to the increased distance from the Sun and the atmosphere. I think that's where the idea of nuclear power plants comes from.

 

[KurtLudwig]

Thank you all for your answers.
In the meantime I did more searching at NASA and reviewing in a physics textbook.
As you know, the radiative heat loss is calculated by the Stephan-Boltzmann Law, S = 5.67x10^-8 times (difference in absolute temperature)^4power. Any activity on the Moon or Mars will require radiative heat removal, such as digging tunnels for habitation and growing food.
Since Mars is further from the Sun than the Moon and photovoltaics will be less efficient in generating electricity, NASA has developed and tested a nuclear powered device to generate electricity. The device consists of a sealed Stirling engine powered by heat from uranium. It will produce power at 10 KW. The device is shielded from the Sun with an large umbrella-type heat shield, to make the thermal radiation more efficient.
Physics really comes into play in space travel and establishing a lunar base.
We all realize the formidable obstacles and huge (astronomical) resources required to eventually establish a permanent base on Mars. It can only be jointly funded by the more prosperous nations over decades.

 

[russ_watters]

Plugging some numbers into a calculator for radiation, I get 4,900 W/sq m for a PWR operating at a return water temperature of 275C.

 

[hutchphd]

Also if the radiation can be contained some part of that heat can probably be used in living quarters and hydroponic gardens on its way out Particularly on Mars I would think. I hope there is good water to be had.

 

[PeroK]

Also if the radiation can be contained some part of that heat can probably be used in living quarters and hydroponic gardens on its way out Particularly on Mars I would think. I hope there is good water to be had.